In an ultimately omitted line of dialogue from the revised final draft script of "Broken Bow", Reed advised a female crewman, who was attempting to fine tune a set of power conduits using a small tool, that she could quicken the process if she "rebalance[d] the polarities." [1]

Tom Paris and Harry Kim tried to find the person who attacked EnsignTabor on the holodeck and Paris had the idea to dampen the photonic ambience and enhance the polarity but was interrupted by Tuvok. (VOY: "Repression")

Harry Kim informed Captain Janeway that he rerouted all available power to the thrusters but wasn't able to free the ship from the Void. Janeway then suggested to reverse the shield polarity. (VOY: "The Void")

"Reversing the polarity" of something is a classic cliché of science fiction "technobabble". It was used long before it was employed in Star Trek. One early antecedent of whom the Berman-era writing staff were clearly aware was Doctor Who, where "reversing the polarity" has been a catch phrase since the early 1970s.